What is the use of mod_ping.erl file? How can we manipulate the sleep time of the server ?

Hi,

First I want to know what is mod_ping.erl file. What does it do . How does it function..?
Secondly I want to know how can I change sleep time of the server. What I want to do is if the server does not receives any request for long time or for a certain time then it should go to sleep.

Please help me.